Industry cases - Industrial wastewater treatment and reuse

—— Comprehensive Problem of "High Intensity, Multiple Sources, Heavy Metals"

The iron and steel metallurgical industry is a typical high-water-consuming and high-pollution industry. Its wastewater comes from a wide range of sources, including coking, sintering, ironmaking, steelmaking, steel rolling, cooling and other links. There are many types of pollutants, and the water quality is complex and fluctuating. It has the following main characteristics:
Multiple water sources and multiple pollution: A large steel plant can discharge more than 10,000–100,000m³ of wastewater per day, involving oily wastewater, cyanide wastewater, acid and alkali wastewater, high-temperature cooling water, slag flushing water, steel rolling emulsion and other water types, with complex and cross-linked components.
High heavy metal content: Contains heavy metal elements such as iron, zinc, lead, chromium, and manganese, with concentrations ranging from several mg/L to hundreds of mg/L, with strong toxicity and difficult biological degradation.
Large pH fluctuations and strong toxicity: The pH range of the wastewater from the acid and alkaline washing processes is large (2–12), and it also contains a large amount of suspended solids, emulsified oil, cyanide, etc., which impacts the subsequent treatment system.
High total salt content and hardness: The total salt concentration in the wastewater can be as high as 2,000–8,000 mg/L, and the Ca²⁺ and Mg²⁺ contents are high, which are easy to scale and clog the treatment equipment and pipelines.